As everyone knows, the optical wave is an electromagnetic wave; when the electromagnetic wave is emitted in a medium such as a fiber, the incident electromagnetic wave will interact with molecules or atoms forming the material, so as to generate scattering spectra, which commonly comprises Rayleigh scattering and Brillouin scattering. By using the scattered light information, people develop a lot of sensing fiber monitoring instruments, but regarding to the currently developed monitoring devices, the actual application of the fiber sensing technology lags far behind the requirement on the technology currently due of the variety of current performance parameters and the requirement of high standard, wherein the fusion sensing fiber technology and the acoustic emission technology are one of the fields lacking research.
In the hydraulic engineering and civil engineering, the interior of the material may have fractures of different degrees under the effects of external temperature, water loading, weight, etc. The fracture is invisible internal damage under many conditions, and if the fracture cannot be detected and found in time, it is possible to develop into a potential safety hazard in the engineering. This defect or damage may have a continuously accumulated and irreversible process with the time, which is possible to cause whole or partial sudden invalidation of the structure, so as to lead to serious engineering problem. The material may release elastic energy in damage, the elastic energy is transmitted in the form of elastic wave in the material, and the elastic wave is called acoustic emission wave.
In order to better guarantee the engineering safety and increase the reliability and stability of the system, it is very important to reduce unnecessary lose and cost, and explore a more advanced detecting and monitoring technology. Since the sensing fiber technology and the acoustic emission technology have good monitoring and detecting performance, the fusion thereof will generate great technical improvement. In order to break through the piezoelectric ceramic acoustic emission detection method with large system, many cables and bad anti-electronic logging interference ability and the current fiber bragg grating acoustic emission testing system of point mode monitoring, the present invention fuses the femtosecond laser optical frequency comb technology and acoustic emission technology, and realizes the monitoring and detecting technology with spatial orientation, whole-course distribution, high spatial resolution and high detecting precision through establishing the new type monitoring and detecting technology fusing the fiber sensing technology of Rayleigh scattering and Brillouin scattering, and the acoustic emission technology. The apparatus and the method have novel setting point, simple structure arrangement, convenient operation and good practical engineering application meaning and scientific researching value.